5th gen cruise

[Scott560]

One thing that has bugged me is the cruise never worked in my newer 5th gen. The switch light goes on, but it never activates the dash light.

Broke out the service guide and the multimeter and started testing it all out. Switches link to ECU seems fine, as does power etc.

Clutch switch was not doing what it should, so I adjusted it until there was continuity when the clutch pedal is up as per the test. Took it for a quick spin. Pressed set, and voila the CC dash light came on. Disengaged it, and it never worked again. Rechecked the clutch switch and still has continuity when up, goes open when pressed down.

Given the awkward location and pain to check laptop and back probe a 14pin multiplug under the dash at the same time, anyone else had any issues with it? Checking every wire and testing it is gonna kill my back so I'm after a quick win lol.

I have 2 spare ecus so I'll give those a go also.

[Scott560]

So with an assistant (the wife) reading out the tests and the pinout from the manual/laptop in the passenger seat, I did all the tests and everything was good except the clutch switch. Intermittent closing of the circuit and limited area of contact over the switches throw area. Obviously worn out over 126k miles of driving (that's a fair number of actuations!)

Now I know hopefully for sure its the switch that's temperamental, i'll bypass it so its always closed circuit, just to check the rest of the system is working fine before splashing out on a new switch - lings honda 40quid not too bad, probably find cheaper on ebay a bit later once i'm satisfied it is just the switch... Some of the resistance values given in the test , mine read much lower. manual gives ranges for the actuator solenoid of 80 - 120 ohm, but i was reading between 40 and 80 (there are 3 of them), ill put that down to the temperature.

Hopefully the last time i have to stick my head under the dashboard!

[Scott560]

Where are the matches?

Took the clutch switch out. Liberal solvents down the business end, actuated many times whilst twisting. Switch behaves like it should. Reinstall into car. Go for a drive. Press set, voila! Light goes on, car drove itself momentarily. Press some buttons, turns off. Never activates again.

Pull over and power cycle the car, cruise master switch still lights up, but CC will never engage...

Get home, check switch is still all good (it is) but to rule it out I hardwire the switch closed on the loom end, and confirm this is rhe case at the back of the ECU multiplug (it was). Reseated the cruise ECU multiplug also. Go out for a drive, CC doesn't activate once.

Will swap out the ECU with a known good one from my old 5th gen.

Also noticed different part number for manual and automatic cruise ECUs, not sure why, pinout is the same and tests are the same (except the clutch switch input is also shared with gear selector on the auto).

Annoyed its not working, even though I'd rarely use it

[Scott560]

I swapped out the cruise ECU for my old 5th gen one, activated first time. Regulated the speed ok , speed up and speed down seemed to work ok. Deactivated the CC, re activated again OK, then turns off and starts not to activate once more. Manage to get it to re-activate twice more during the journey, confirmed that pressing the clutch or brake deactivates it. (clutch switch is no longer hard bypassed at this point)

This is a known good ecu from my last car - so i'm leaning towards something car side being the cause. Running out of ideas but have a few more to test.

1) osciloscope on the speed wire into the cruise ECU - check that the speed pulse is consistent with wheel speed - perhaps the CC is unwilling to engage if it believe the speed is not constant - although id expect my speedometer to show similar)

2) rear spoiler led lights have been added retrospectively - possibly interfering with the brake signal input to ecu? LEDs can produce voltage in sunlight.

3) i do have a spare cruise actuator, but would expect a fault to be open circuit or not something that would deactivate the cruise ECU - there is nothing in the service manual i could see about CC fault codes (unlike ABS/SRS/ECU/4WS codes).

Anyone else got any thoughts?

[Scott560]

Right, making progress now! Since the clutch switch is deffo sorted via cleaning and adjustment, the temperamental nature of it engaging seems to now rest on the brake pedal switch. If I pull up on the brake pedal, it will engage every time. The slightest touch of the pedal, or a bump or a sneeze seems to disengage it.

Disconnecting the rear led middle brake light made no difference, although I had read elsewhere it can be a factor, so reconnected, no difference, issue still seems to rest solely on the brake switch.

So lessons learned - can't always trust the multimeter in high impedance mode to act/behave like the receiving circuit. Switches are noisy, multimeter won't show you that...

Second lesson - you may have more than one fault, so keep testing until you have none left!

Was just about to give up as far too hot today to be faffing!

Cheers

Scott

[indigolemon]

Glad you got to the bottom of it! Those switches are definitely the usual problem, as they are being actuated even when the CC isn't engaged.

[ek9sid]

I was going to say it definitely seems like a switch issue. I had an issue on my old daily drive (Vectra) where the cruise would shut off intermittently. It turns out the slave cylinder was leaking, and as a result the clutch pedal wasn't as solid. Thus, whenever cruise was activated it would shut off whenever you went over the slightest bump.

The biggest pain to this was that the slave cylinder was mounted inside the gearbox. So after a while, the clutch fluid started to cause the clutch to slip. And also, to change it was a gearbox off job - which was also a subframe off job. Getting the subframe back on was the biggest ballache. Obviously clutch and dual mass was done at the same time.

The only issue my prelude had with the cruise was a stiff throttle cable causing the cruise to react really sluggish.

(Sorry for going off on a tangent).

[Scott560]

All sorted now thankfully. Cleaned up the brake switch in the usual manner with some lighter fluid down the inside of the plunger , and some actuations to clean it up. Reinstalled/adjusted, put the old ECU back in, all works great. Very little travel on the brake pedal though until it disengages, but at least it won't turn off at random now.

Still annoyed that following the book method of using a multimeter to test the inputs to the ECU can fail - switch just wasn't making enough of a connection for the ECU to be happy, but enough to set the multimeter beep off.

Ho hum - live and learn...

And yeah - sod the vectra

[Vtecmec]

Great work, you've inspired me to fix mine now.....

[Scott560]

Great work, you've inspired me to fix mine now.....

Yeah, hopefully with the lockdown people are finding a little more time. I'm still full time working from home , but no travel time, and a week off in Easter meant I could catch up on a lot of jobs...